Configure an iMac Pro for Video Editing [u]

[ Update: On March 19, 2019, Apple released updates to the iMac Pro. The new system features expanded RAM and an updated GPU option. While the new system improves performance, the recommendations in this article remain unchanged. ]

Ever since Apple released the iMac Pro, my email has been clogged with people asking advice on how to configure their system. So, I did some research and here’s what I learned.

This article is designed to help you make more informed decisions when you don’t have an unlimited budget. Also, the iMac Pro is designed for many different markets. In this article, I’m just focusing on digital media.

If money is no object, buy the top of the line. It will be blindingly fast, it will work great and you’ll have enormous bragging rights.

But, if money IS an object, then you need to make trade-offs, balancing the performance you need with the money you have.

The good news is that you don’t need to buy the top-of-the-line to get a system today that can meet your editing needs for the next several years.

SOME BACKGROUND

When Apple rebuilt Final Cut to create FCP X, they focused on upgrading its underlying architecture to take advantage of coming advances in hardware. This includes an all-64-bit architecture, optimization for core technologies including Metal, tight integration with both CPU and GPU, and the ability to take advantage of faster i/o – both to the processors and storage.

There are no optimizations in Final Cut, Motion or Compressor that focus specifically on the iMac Pro. Instead, Apple’s media apps take advantage of whatever technology or performance benefits are provided in the hardware.

In other words, there are no new features in FCP X that appear if it is running on an iMac Pro. What does appear is faster performance.

Apple’s website states:

iMac Pro takes Mac performance to a whole new level, even when compared to our fastest quad-core iMac.

Photographers can work with enormous files and perform image processing up to 4.1 times faster.

Music producers can bounce (export) massive multi-track projects up to 4.6 times faster and use up to 12.4 times as many real-time plug-ins.

Video editors can edit up to eight streams of 4K video, or edit 4.5K RED RAW video and 8K ProRes 4444 at full resolution in real time without rendering. The iMac Pro can also export HEVC video 3 times faster.

In other words, these numbers are based on the high-end 18-core system, which won’t be shipping until next year and, as you’ll see, may be more than you need.

DO YOU REALLY NEED AN IMAC PRO?

Well, “need” is a relative term. If you principally work with SD or HD material, an iMac will be perfectly fine. The performance benefits of the iMac Pro don’t justify the expense.

If you are hobbyist, no, you don’t need an iMac Pro. This is not the same as not wanting one, but you don’t need it.

However, if the bulk of your work involves 4K or greater frame sizes, 360° VR, RAW files, or HDR, the performance benefits of this new system make it worth considering, because the design of the iMac Pro significantly speeds working with larger frame sizes, faster frame rates, more effects, more processor-intensive codecs (such as HEVC).

With that being said, let’s take a look at the specific components to see which ones make the most sense for video editing.

DISPLAY

The iMac Pro uses the same display technology as the 5K iMac. So everything you see on a current iMac looks the same on the iMac Pro:

5K display

One billion colors

P3 wide color gamut

500 nits

But, while the display of the iMac Pro is the same as an iMac, the display capability of the iMac Pro is greater:

It can drive two other 5K displays or up to four other 4K displays.

It has enhanced external connectivity and more Thunderbolt 3 ports (so you still have Thunderbolt ports left over for other accessories after connecting a display).

CPUs

Before the shouting starts, let me say again that if money is no object, buy the top-of-the-line iMac Pro. However, for most of the editing that most of us are doing, we don’t need to buy the top-of-the-line system to get significantly improved editing performance.

The 8-core system is fine for most editing and compression. For example, H.264 compression takes advantage of a hardware encoder which is built into all current Macs. This hardware encoder is independent of CPU cores.

However, there are benefits to more cores, especially when decoding and encoding heavily threaded codecs like ProRes or HEVC. Also, the 10-core system offers a higher Turbo Boost speed of 4.5GHz versus 4.2GHz for the 8-core CPU. This additional speed benefits rendering and exporting.

The 14 and 18 core systems are designed for other applications than video editing. I would invest my money elsewhere in the system because video editors will see greater benefits in upgrading RAM and GPU when using Final Cut Pro on an iMac Pro.

An exception to staying within a 10-core system is that editors using RED RAW media or working with multiple streams of ProRes — for example, multicam work — will see improved performance with higher-core systems.

One of the issues I’ve heard about the current Mac Pro is that it has a problem with heat under heavy load. What I discovered is that, even more than the Mac Pro, the iMac Pro internals are designed specifically to dissipate heat under heavy load.

Outside, the iMac Pro is millimeter for millimeter the same size and shape as a standard 27-inch iMac with Retina 5K display; outside of the space gray color and a few extra vents on the back. But, on the inside, it’s radically different.

One of the key things Apple was able to do is make the system all flash-based; 3 GB/s of fast SSD is pretty darn fast! Switching to all flash allowed Apple to remove the 3.5” hard drive and use that large space for a dual blower design and a massive heatsink and heat pipe architecture.

This delivers 75% more airflow and 80% more thermal capacity, enabling far more CPU and GPU power in the box over a traditional iMac. It is also worth noting that it does all this while still being super quiet (it is an iMac, after all), letting you focus on your work.

GPUs

In general, editing video tends to use more of the CPU while effects and graphics tend to rely more heavily on the GPU. Increasingly, both FCP X and Premiere rely on the GPU for more and more tasks. Also, the greater the VRAM, the better the GPU performance.

Whether you use Motion, After Effects, Premiere or Final Cut, investing in the best GPU will be a wise choice.

NOTE: While VRAM is important, VRAM is not the only determinant of a superior graphics card. For example, the Vega 64 is significantly faster in addition to the larger amount of VRAM. Also, more VRAM offers benefits when working with large frame sizes, multiple video streams (i.e. multicam), multiple displays, and complex motion graphics.

UPDATE: It important to note that buying a better GPU does not improve image quality. What it does, instead, is work faster. Specifically, faster rendering and exporting. If time is scarce, an updated GPU will speed effects rendering, exporting and, in some cases, video compression.

RAM

The 32 GB default RAM is fine for virtually all editing. If, on the other hand, you run multiple applications at once – say FCP X, Motion, Compressor, Photoshop and a web browser – 64 GB of RAM is better.

While there is value in more RAM beyond 64 GB, you won’t get enough bang for your buck to justify the additional cost.

Larry’s recommendation: 32 GB for people on budgets, with a maximum of 64 GB for serious multi-application users.

The iMac Pro ships with a 1 TB SSD. I have’t measured it, but it is probably way past blindingly fast. (Apple says 3 GB/second!) The problem is that most media projects today far exceed 1 TB in storage. You will need an external high-speed, Thunderbolt 3 RAID system for even medium-sized projects.

Unlike video editing, video compression has its own requirements for system resources. While this is worth its own article here are some thoughts.

Both H.264 and HEVC are relatively highly compressed formats. This compression, of course, leads to smaller file sizes, but the resulting compression requires more processing power. With H.264 and HEVC, decoding and most encoding actions are processed via dedicated H.264 hardware within the system.

NOTE: A select set of custom H.264 encodes in Compressor may use the H.264 software encoder, which is threaded across multiple cores.

So while ProRes encoding benefits from faster, higher-core CPUs, H.264 and HEVC are not similarly CPU bound. Also, it’s important to note that video compression often includes other operations including retiming, scaling, and color conversion — all of which use the GPU.

If you are interested in HDR, 8-bit HEVC does, in fact, support HDR. Still, 10-bit encoding is recommended for the highest quality HDR output when using the HEVC codec. The reason this is important is that current Macs only support hardware acceleration of 8-bit HEVC. This makes the iMac Pro about 3x faster in HEVC encoding than an iMac.

For 10-bit encoding, the HEVC software codec is threaded and can therefore take advantage of multiple CPU cores when encoding; more cores means faster video encoding.

WAIT, WHAT ABOUT THE MAC PRO?

First, Apple has announced and reiterated that they are working on a new, modular Mac Pro. However, they haven’t announced specs nor a release date.

The current Mac Pro is getting long in the tooth. In terms of performance, the iMac Pro is a better choice.

That being said, there are still two reasons to consider the existing Mac Pro:

You can add any monitor you want

Many of the components inside are upgradeable

For me, while these benefits are not trivial, the hardware inside the system has not be upgraded in several years. If you are focused on video editing, the existing Mac Pro is not the best current choice.

SUMMARY

Here are my two recommendations for an iMac Pro for video editing: a budget version and a “top-of-the-line-for-editors” version. (The mouse and keyboard come standard, I make no recommendations about either of these.)

Here’s the short answer: your quality will be the same, regardless of the gear you buy. So, if you are not on deadlines, you can spend less. If you are on tight deadlines, you need to spend more.

* H.265 is really hard to edit, I would recommend 10 core. 8-core will work, however, if your budget is tight. * 32 GB of RAM is fine. You can add more later if you need it. * You didn’t say if you were doing lot of effects, so you don’t need a high-end GPU * 10 core is also better for video compression

In general, this would be more than enough. Keep in mind that the GPU is not used for editing, but for rendering and effects.

HOWEVER!!! It is totally possible to create a multicam edit which no system can edit natively. For example, 20 streams of 4K RAW files will bring both your storage and computer to its knees.

Remember, the bandwidth of your storage is determined both by the protocol (Thunderbolt 3), the type of devices it contains (spinning media or SSD) and the number of devices (more is faster). It is possible for your storage not to be fast enough to support a massive number of clips in a multicam edit.

Proxies are still your friend – even for multicam edits. I recommend using them for large multicam projects because they will allow yourself to get work done faster.

I push video equipment and video editing to the limits, but not in normal ways. My challenges are not with 4K and up (though I understand why this is important), but how to reduce the cost and time requirements of prodigious amounts of 1080 HD compression and down-res work.

I work with small inshore fishing boats, trialling the use of automated video to make fish stock assessments (and other issues relating to the sustainability of the fish) better and cheaper. It’s important because the video coverage now coming in on large offshore vessels cost multiple $100s a day, more than the value of most small day-boat inshore boats’ catches. But if we can’t solve this it puts the survival of the inshore industry at risk as the (reasonable) demands for better data to permit fishing increase. As day-boats only make up 10% of all landings, they often don’t have much clout nationally, but they are hugely important to local communities and those who get the benefit of the (ultra-fresh) fish.

Currently we are piloting equipment with the capacity to cope with video from 10 vessels per day each providing up to 14 hours of 1080 HD video using Garmin VIRB Ultras, which also provide essential GPS data. So that means up to 140 hrs of video per day, around 2TB every day. If successful we will need to deal with more than 10 boats.

When that video comes in we need to:

1) downres a copy of all video to 480 SD, because we need to preserve – at least for a couple of months/years – an entire record of each trip from the boats, from power up to power down. Minimising the terabytes is the key issue here, image quality less important but not unimportant.

2) we also use the GPS data (boat speed) to detect when the boats are actually fishing, and use that to quickly strip out just that fishing video, perhaps 3-4 hours per trip per boat. That also needs to be compressed, but here image quality is important, so the resolution is maintained at 1080 and the trade off in compression is in favour of greater image quality. This video is then quantified – essentially to count, identify and measure fish – by researchers, either us or clents

Currently 2) quantification is done by humans, but this video will also:

3) be used to see if we can train computers to count, recognise and measure fish. For AI we will in addition go back to the original 2-4 hours fishing video off the cameras and extract the individual frames, to provide a set of training images from the stills..

My impression is that most of the current attention is on accelerating 4K and 8K video workflows. For us, paying out even $40k for a maxed out Mac Pro isn’t necessarily a problem, if the equipment can be worked to capacity and it allows a human to cope more economically with processing more video and more boats. But I am finding it difficult to get a sense of how much faster, if at all, iMac Pros or 2019 Mac Pros, are going to make a 1080 workflow (and 1080 > 480 down-res) compared to, say, top of the range 2018 iMacs and MacBook Pros that I am familiar with. If all of the attention is going into hardware to accelerate 4K and 8K workflows, perhaps not as much as I would like?

If there are resources dealing with current hardware speeds, re 1080/ 1080> downres I’ve not found them.

Do you have any sense about what difference it will make – even order of magnitude stuff.

Any thoughts from you or the community much appreciated, Malcolm

Ps when I started this I thought offloading from microSD cards was going to be a bottleneck – but it isn’t with UBS-C where it is possible to offload 4 x 128 GB 128 MB/s read time microSD cards in 7 mins (although a card from one brand melted in the card reader), or 1 TB 160 MB/s cards with an entire week’s fishing activity in 2 minimally supervised hours.

This is a fascinating note. Thanks for writing. It is impossible, at this point, to know for sure what the capabilities of the 2019 Mac Pro will be. Apple has not released enough information for us to know. Until they do, I would hold off making and hardware purchases.

Three key points to keep in mind:

* The codec – and bit rate – you are compressing into makes a BIG! difference in speed and image quality. * Computers that support hardware acceleration for the codec you are using will be 10X faster than the same compression in software * There are affordable, automated tools that can help simplify this process. Three to look at include: KeyFlow Pro (probably your best option), Kyno, and Axel.ai.

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